1. Field of the Invention
The present invention relates to a method of regulating the resonance frequency of a surface-mountable antenna which is employable with a mobile communication device or the like.
2. Description of the Background Art
The structures of conventional surface-mountable antennas are now described with reference to FIGS. 4 and 5 showing perspective views of such antennas 1 and 11.
Referring to FIG. 4, the surface-mountable antenna 1 comprises a substrate 2 which is made of a dielectric material such as ceramic. The substrate 2 is provided on its upper surface 2c with a groove 3 having end portions 3a and 3b at a pair of opposite end surfaces 2a and 2b respectively. A conductor is applied to the inner peripheral surface of the groove 3, thereby forming a radiating electrode 4. Further, a conductor is applied around the end portion 3a of the groove 3 on the end surface 2a of the substrate 2, thereby forming a feeding electrode 5 in connected to the radiating electrode 4. In addition, conductors are applied to both end portions of the end surface 2a of the substrate 2, thereby forming ground electrodes 6 insulated from the feeding electrode 5. Further, a conductor is applied to the overall end surface 2b of the substrate 2, thereby forming an end electrode 7.
In the surface-mountable antenna 1 having the aforementioned structure, the resonance frequency and the frequency bandwidth are decided by a capacitance component which is formed by the ground electrodes 6 and the end electrode 7 and an inductance component which is present in the radiating electrode 4, so that the radiating electrode 4 transmits/receives electric waves.
Referring to FIG. 5, on the other hand, the surface-mountable antenna 11 comprises a substrate 12 which is made of a dielectric material such as ceramic. The substrate 12 is provided with a through hole 13 having opening portions 13a and 13b at a pair of opposite end surfaces 12a and 12b respectively. A conductor is applied to the inner peripheral surface of the through hole 13, thereby forming a radiating electrode 14. Further, a conductor is applied around the opening portion 13a of the through hole 13 which is formed at the side surface 12a of the substrate 12, thereby forming a feeding electrode 15 connected with the radiating electrode 14. In addition, conductors are applied to both end portions of the end surface 12a of the substrate 12, thereby forming ground electrodes 16 insulated from the feeding electrode 15. Further, a conductor is applied to the overall end surface 12b of the substrate 12, thereby forming and end electrode 17.
In the surface-mountable antenna 11 having the aforementioned structure, the resonance frequency and the frequency bandwidth are decided by a capacitance component which is formed by the ground electrodes 16 and the end electrode 17 and an inductance component which is present in the radiating electrode 14, so that the radiating electrode 14 transmits/receive electric waves.
In measurement of the resonance frequency, the surface-mountable antenna 1 or 11 is mounted on a substrate (not shown) and connected to a measuring device (not shown) such as a network analyzer. If a desired resonance frequency is not attained as the result of such measurement, this antenna is regarded as a defective, assuming no regulation of the resonance frequency possible.
If every such surface-mountable antenna which cannot attain a desired resonance frequency is regarded as a defective unit, however, the non-defective yield of the surface-mountable antenna is disadvantageously reduced, which increases the effective cost of each non-defective unit.